Week 10 - Ischaemic Heart Disease Flashcards
What are the risk factors for coronary atheroma?
Non-modifiable: - Increasing age - Male gender (females catch up after menopause) - Family history Modifiable: - Hyperlipidaemia - Cigarette smoking - Hypertension - Diabetes mellitus - Exercise, obesity, stress (less important)
What are the differences between a stable and vulnerable plaque?
- Stable: small necrotic centre, thick fibrous cap, cap less likely to fissure/rupture
- Vulnerable: large necrotic centre, thin fibrous cap, cap more likely to fissure/rupture
What is ischaemic chest pain?
Any IHD can cause chest pain that is central, retrosternal or left-side
- Pain may also radiate to the shoulders and arms, along with the neck, jaw, epigastrium and back (can present here without chest pain)
- Pain = tightening, heavy, crushing, constricting
- Pain varies in intensity and duration
- Pain onset, precipitating, aggravating and relieving factors and associated symptoms all vary
- Gets progressively worse from stable angina, to unstable angina, to MI
What is stable angina?
- Atheromatous plaques build up in the coronary vessels
- – The plaques have a necrotic centre and fibrous cap
- – Occlude more and more of the lumen, leading to ischaemia of the myocardium
- Angina occurs when the plaque occludes >70% of lumen
- Flow is sufficient at rest, so pain is relieved when demand stops
- Transient ischaemia during periods of increased O2 demand
- May progress gradually over time
- Mild-moderate pain
- No myocyte injury or necrosis
How can you treat stable angina?
- Acute episodes: sublingual nitrate spray/tablet (venodilates, deduces preload)
- Prevent episodes: ß-blocker (decrease heart rate and contractility), Ca2+ channel blockers (decrease after load by peripheral vasodilation)
- Oral nitrates
- Prevent cardiac events: aspirin (decreased platelet aggregation so decreased thrombus formation if plaque is disrupted), statins (decrease LDL cholesterol, decrease progression of atherosclerosis, increase plaque stability)
- Long term: consider revasculatisation (mechanically restores blood flow using coronary angioplasty and stenting)
How do you investigate stable angina?
Clinical diagnosis:
- Based on history
- No specific signs on examination
- May have risk factors (high BP, corneal arcus)
- Signs of atheroma elsewhere
Resting ECG:
- Usually normal
- May show signs of previous MI
Exercise stress test to confirm diagnosis:
- Graded exercise on a treadmill connected to an ECG until either:
— Target heart rate is reached
— Chest pain occurs
— ECG changes
— Other problems (e.g. Arrhythmia)
- Test is positive if ECG shows ST depressions of >1mm
What is unstable angina?
As angina worsens due to the profession of the formation of the atheromatous plaque, it progresses from stable to unstable angina
- Due to increased lumen occlusion
- Classified as Ischaemic chest pain that occurs at rest
- Severe pain
- Occurs with a crescendo pattern
What is acute coronary syndrome?
Sudden plaque fissuring with thrombus formation
- Relates to a group of symptoms attributed to the obstruction of the coronary arteries
- If occlusion is complete and persistent, and a large area of myocardium without collateral circulation is affected, it will result in STEMI
- If there is a non-occlusive thrombus, brief occlusion, collaterals present and a small area of myocardium is affected, then is results in NSTEMI or unstable angina
What is a myocardial infarction?
- A complete occlusion of a coronary vessel, leading to an infarct of the myocardium it supplies
- The fibrous cap of the atheromatous plaque can undergo erosion or fissuring, exposing blood to the thrombogrnic material in the necrotic core
- The platelet ‘clot’ is followed by a fibrin thrombus which can either occludes even entire vessel where it forms or break off to form an embolism
- Typically presents with ischaemic chest pain
- Pain is very severe, persistent pm at rest, often has no precipitate
- Pain is not relieved by rest or nitrate spray
- Patient may be breathless, faint, sweating, nauseous, vomiting and have pallor
What is NSTEMI?
Non ST elevated MI
- Infarct is not full thickness of the myocardium
- ST depression
- Partial/brief occlusion or adequate collateral circulation
- Injury limited to more vulnerable sub-endocardial areas
What is STEMI?
ST elevated MI
- Infarct is full thickness of myocardium
- Most have total occlusion of an artery
- Injury extends to dub epicardial side
What are the signs/symptoms of MI?
- Patient is anxious/distressed
- Sweating, pallor
- Cold, clammy skin
- Tachycardia/arrhythmias
- Low BP
- Signs of heart failure
What are the ECG changes during a STEMI?
- Hyperacute T wave
- ST elevation
- Q wave
- ST-elevation with T wave inversion
- T wave recovery
How can you identify a previous MI on an ECG?
Via the persistence of the pathological, deepened Q wave
What are the principles of management of angina, acute MI and unstable angina?
- Prevent thrombosis (anti-platelet drugs, anticoagulants)
- Dissolve thrombus (fibrinolytic agents)
How is unstable angina/MI treated?
- Prevent progression of thrombosis
- Restore perfusion of partially occluded vessels
- – If high risk: early percutaneous coronary intervention or coronary artery bypass graft
- – If low risk: initially medical treatment
- Pain control, O2, organic nitrates, beta-blockers, statins, ACE inhibitors
What is the long-term treatment following MI?
- Aspirin = decreased mortality and re-infarction
What are the common causes of chest pain?
Heart and great vessels: - Central pain - Ischaemic myocardium - Pericarditis - Aortic dissection Lungs and pleura: - Pneumonia - Pneumothorax - Pulmonary embolism GI system: - Chest and epigastric pain - Oesophagus (reflux) - Peptic ulcer disease - Gall bladder (buliary colic, cholecystisis) Chest wall - Localised pain, may increase on movement - Ribs (bone metastases, fractures) - Muscles - Skin - May be due to trauma
What is an angiography used for?
To view any vessel conclusions
- From the findings choices can be made about revasculaisation surgeries
What is percutaneous coronary intervention?
Angioplasty and stenting
- Inflation of a balloon inside the occluded vessel expands a mesh that holds the vessel open
- This increases the lumen size allowing more blood to flow through
What is coronary bypass grafting?
Involves taking an artery from elsewhere in the body and grafting it to the heart
What are the causes of acute pericarditis?
- Infections
- Post MI/cardiac surgery
- Autoimmune
- Uraemia (kidney failure)
- Malignant deposits
What are the symptoms of acute pericarditis?
- Central/left-sided chest pain
- Sharp, worse than inspiration
- Improved by leaning forward
Which biomarkers can be used in the diagnosis of MI?
Troponins - Cardiac troponin and troponin T are proteins important in actin/myosin interaction - Very sensitive and specific marker - Released in myocyte death - Levels decline slowly (10-14 days) Creatine kinase - 3 isoenzymes present in the skeletal muscle, heart and brain - CK-MB is the cardiac isoenzyme - Levels return to normal in 48-72 hours
What does the presence of cardiac biomarkers in the blood show?
It shows that there has been death of the myocardium
